Thanks for the updates. Interesting theories. I do not have backfires with mine like you did. Mine runs exceptionally great cold for about 10 minutes. Revs to redline smooth and fast. Faster than I want to go in a 53 year old truck with warn steering box and manual brakes and warn shocks! But after that 10 minutes or so it will stumble badly with even just a small acceleration. Tried regarding and advancing timing no real effect on it. It still drives ok when not accelerating. Under load 1 or 2 cylinders seems to go out. Let it cool down a couple hours and it runs great again for 10 minutes. Got to work on it soon. Got new parts but no time.
